Since cubic boron nitride (hereinafter, also referred to as “cBN”) has a high hardness, a sintered compact obtained by sintering cubic boron nitride together with a binding material such as ZrO2 or Al2O3 has been used for tools such as a cutting tool (WO 2008/087940 (Patent Document 1), WO 2011/059020 (Patent Document 2), WO 2012/029440 (Patent Document 3), and WO 2012/057184 (Patent Document 4)).